import java.io.IOException;
import java.net.DatagramPacket;
import java.net.DatagramSocket;
import java.net.Socket;
import java.net.SocketException;

public class UdpEchoServer {
    private DatagramSocket socket  ;
    public UdpEchoServer(int port) throws SocketException {
       this.socket = new DatagramSocket(port);
    }
    public void start() throws IOException {
        System.out.println("服务器上线");
        while (true){
            DatagramPacket requestPacket = new DatagramPacket(new byte[4096] , 0 , 4096) ;
            socket.receive(requestPacket);
            String request = new String(requestPacket.getData() , 0 , requestPacket.getLength());
             String response = process(request);
            DatagramPacket responsePacket = new DatagramPacket(response.getBytes(),0 , response.getBytes().length
              , requestPacket.getAddress() , requestPacket.getPort());
            socket.send(responsePacket);
            System.out.println("ip:"+requestPacket.getSocketAddress().toString() +"port: "+ requestPacket.getPort()
                     +"请求:"+request+" "+response);
        }
    }

    private String process(String request) {
    return "响应: "+request;
    }

    public static void main(String[] args) throws IOException {
        UdpEchoServer server = new UdpEchoServer(7077);
        server.start();
    }

}
